scholarly journals MICRURGICAL STUDIES IN CELL PHYSIOLOGY

1926 ◽  
Vol 8 (4) ◽  
pp. 369-401 ◽  
Author(s):  
Robert Chambers ◽  
Paul Reznikoff
Keyword(s):  
Surface Membrane ◽  
Surrounding Medium ◽  
Lethal Effect ◽  
Great Difficulty ◽  
Amoeba Proteus ◽  
Cell Physiology ◽  
Appreciable Effect ◽  
Disruptive Effect ◽  
Liquid Sphere ◽  
A Cell

By means of micro-dissection and injection Amœba proteus was treated with the chlorides of Na, K, Ca, and Mg alone, in combination, and with variations of pH. I. The Plasmalemma. 1. NaCl weakens and disrupts the surface membrane of the ameba. Tearing the membrane accelerates the disruption which spreads rapidly from the site of the tear. KCl has no disruptive effect on the membrane but renders it adhesive. 2. MgCl2 and CaCl2 have no appreciable effect on the integrity of the surface membrane of the ameba when applied on the outside. No spread of disruption occurs when the membrane is torn in these salts. When these salts are introduced into the ameba they render the pellicle of the involved region rigid. II. The Internal Protoplasm. 3. Injected water either diffuses through the protoplasm or becomes localized in a hyaline blister. Large amounts when rapidly injected produce a "rushing effect". 4. HCl at pH 1.8 solidifies the internal protoplasm and at pH 2.2 causes solidification only after several successive injections. The effect of the subsequent injections may be due to the neutralization of the cell-buffers by the first injection. 5. NaCl and KCl increase the fluidity of the internal protoplasm and induce quiescence. 6. CaCl2 and MgCl2 to a lesser extent solidify the internal protoplasm. With CaCl2 the solidification tends to be localized. With MgCl2 it tends to spread. The injection of CaCl2 accelerates movement in the regions not solidified whereas the injection of MgCl2 induces quiescence. III. Pinching-Off Reaction. 7. A hyaline blister produced by the injection of water may be pinched off. The pinched-off blister is a liquid sphere surrounded by a pellicle. 8. Pinching off always takes place with injections of HCl when the injected region is solidified. 9. The injection of CaCl2 usually results in the pinching off of the portion solidified. The rate of pinching off varies with the concentration of the salt. The injection of MgCl2 does not cause pinching off. IV. Reparability of Torn Surfaces. 10. The repair of a torn surface takes place readily in distilled water. In the different salt solutions, reparability varies specifically with each salt, with the concentration of the salt, and with the extent of the tear. In NaCl and in KCl repair occurs less readily than in water. In MgCl2 repair takes place with great difficulty. In CaCl2 a proper estimate of the process of repair is complicated by the pinching-off phenomenon. However, CaCl2 is the only salt found to increase the mobility of the plasmalemma, and this presumably enhances its reparability. 11. The repair of the surface is probably a function of the internal protoplasm and depends upon an interaction of the protoplasm with the surrounding medium. V. Permeability. 12. NaCl and KCl readily penetrate the ameba from the exterior. CaCl2 and MgCl2 do not. 13. All four salts when injected into an ameba readily diffuse through the internal protoplasm. In the case of CaCl2 the diffusion may be arrested by the pinching-off process. VI. Toxicity. 14. NaCl and KCl are more toxic to the exterior of the cell than to the interior, and the reverse is true for CaCl2 and MgCl2. 15. The relative non-toxicity of injected NaCl to the interior of the ameba is not necessarily due to its diffusion outward from the cell. 16. HCl is much more toxic to the exterior of a cell than to the interior; at pH 5.5 it is toxic to the surface whereas at pH 2.5 it is not toxic to the interior. NaOH to pH 9.8 is not toxic either to the surface or to the interior. VII. Antagonism. 17. The toxic effects of NaCl and of KCl on the exterior of the cell can be antagonized by CaCl2 and this antagonism occurs at the surface. Although the lethal effect of NaCl is thus antagonized, NaCl still penetrates but at a slower rate than if the ameba were immersed in a solution of this salt alone. 18. NaCl and HCl are mutually antagonistic in the interior of the ameba. No antagonism between the salts and HCl was found on the exterior of the ameba. No antagonism between the salts and NaOH was found on the interior or exterior of the ameba. 19. The pinching-off phenomenon can be antagonized by NaCl or by KCl, and the rate of the retardation of the pinching-off process varies with the concentration of the antagonizing salt. 20. The prevention of repair of a torn membrane by toxic solutions of NaCl or KCl can be antagonized by CaCl2. These experiments show directly the marked difference between the interior and the exterior of the cell in their behavior toward the chlorides of Na, K, Ca, and Mg.

scholarly journals MICRURGICAL STUDIES IN CELL PHYSIOLOGY

1926 ◽  
Vol 10 (1) ◽  
pp. 9-21 ◽  
Author(s):  
Paul Reznikoff
Keyword(s):  
Heavy Metals ◽  
Metal Cation ◽  
Surface Membrane ◽  
The Other ◽  
Contractile Vacuole ◽  
Toxic Action ◽  
Cell Physiology ◽  
Relative Toxicity ◽  
A Cell

I. Plasmalemma. 1. The order of toxicity of the salts used in these experiments on the surface membrane of a cell, taking as a criterion viability of amebæ immersed in solutions for 1 day, is HgCl2, FeCl3> AlCl3> CuCl2> PbCl2> FeCl2. Using viability for 5 days as a criterion, the order of toxicity is PbCl2> CuCl2> HgCl2> AlCl3> FeCl3> FeCl2. 2. The rate of toxicity is in the order FeCl3> HgCl2> AlCl3> FeCl2> CuCl2> PbCl2. 3. The ability of amebæ to recover from a marked tear of the plasmalemma in the solutions of the salts occurred in the following order: AlCl3> PbCl2> FeCl2> CuCl2> FeCl3> HgCl2. II. Internal Protoplasm. 4. The relative toxicity of the salts on the internal protoplasm, judged by the recovery of the amebæ from large injections and the range over which these salts can cause coagulation of the internal protoplasm, is in the following order: PbCl2> CuCl2> FeCl3> HgCl2> FeCl2> AlCl3. 5. AlCl3 in concentrations between M/32 and M/250 causes a marked temporary enlargement of the contractile vacuole. FeCl2, FeCl3, and CuCl3 produce a slight enlargement of the vacuole. 6. PbCl2, in concentrations used in these experiments, appears to form a different type of combination with the internal protoplasm than do the other salts. III. Permeability. 7. Using the similarity in appearance of the internal protoplasm after injection and after immersion to indicate that the surface is permeable to a substance in which the ameba is immersed, it is concluded that AlCl3 can easily penetrate the intact plasmalemma. CuCl2 also seems to have some penetrating power. None of the other salts studied give visible internal evidence of penetrability into the ameba. IV. Toxicity. 8. The toxic action of the chlorides of the heavy metals used in these experiments, and of aluminum, is exerted principally upon the surface of the cell and is due not only to the action of the metal cation but also to acid which is produced by hydrolysis.

Linear electrical properties of striated muscle fibres observed with intracellular electrodes

1964 ◽  
Vol 160 (978) ◽  
pp. 69-123 ◽  
Keyword(s):  
Electrical Properties ◽  
Striated Muscle ◽  
Surface Membrane ◽  
Fibre Surface ◽  
Step Function ◽  
Muscle Fibres ◽  
Appreciable Effect ◽  
Current Application ◽  
Current Path ◽  
Wide Range

The linear electrical properties of muscle fibres have been examined using intracellular electrodes for a. c. measurements and analyzing observations on the basis of cable theory. The measurements have covered the frequency range 1 c/s to 10 kc/s. Comparison of the theory for the circular cylindrical fibre with that for the ideal, one-dimensional cable indicates that, under the conditions of the experiments, no serious error would be introduced in the analysis by the geometrical idealization. The impedance locus for frog sartorius and crayfish limb muscle fibres deviates over a wide range of frequencies from that expected for a simple model in which the current path between the inside and the outside of the fibre consists only of a resistance and a capacitance in parallel. A good fit of the experimental results on frog fibres is obtained if the inside-outside admittance is considered to contain, in addition to the parallel elements R m = 3100 Ωcm 2 and C m = 2.6 μF/cm 2 , another path composed of a resistance R e = 330 Ωcm 2 in series with a capacitance C e = 4.1 μF/cm 2 , all referred to unit area of fibre surface. The impedance behaviour of crayfish fibres can be described by a similar model, the corresponding values being R m = 680 Ωcm 2 , C m = 3.9 μF/cm 2 , R e = 35 Ωcm 2 , C e = 17 μF/cm 2 . The response of frog fibres to a step-function current (with the points of voltage recording and current application close together) has been analyzed in terms of the above two-time constant model, and it is shown that neglecting the series resistance would have an appreciable effect on the agreement between theory and experiment only at times less than the halftime of rise of the response. The elements R m and C m are presumed to represent properties of the surface membrane of the fibre. R e and C e are thought to arise not at the surface, but to be indicative of a separate current path from the myoplasm through an intracellular system of channels to the exterior. In the case of crayfish fibres, it is possible that R e (when referred to unit volume) would be a measure of the resistivity of the interior of the channels, and C e the capacitance across the walls of the channels. In the case of frog fibres, it is suggested that the elements R e , C e arise from the properties of adjacent membranes of the triads in the sarcoplasmic reticulum . The possibility is considered that the potential difference across the capacitance C e may control the initiation of contraction.

scholarly journals The secretory pathway of bovine platelets

Blood ◽  
1987 ◽  
Vol 69 (3) ◽  
pp. 878-885 ◽  
Author(s):  
JG White
Keyword(s):  
Plasma Membrane ◽  
Secretory Pathway ◽  
Human Platelet ◽  
Surface Membrane ◽  
Surrounding Medium ◽  
Human Platelets ◽  
Resting Cells ◽  
Granule Secretion ◽  
New Perspective ◽  
Platelet Secretion

Abstract Human platelets contain tortuous channels in their cytoplasm, the surface-connected or open canalicular system (OCS), that communicate directly with the surrounding medium through openings on the surface membrane. Some workers have suggested that the OCS serves as the egress route for products secreted during the release reaction. Others have proposed alternate secretory pathways. Since bovine platelets lack the OCS found in human cells, the present study has examined the secretory mechanism of these cells to see whether it can shed light on the mystery of human platelet secretion. Bovine platelet granules, in contrast to human granules, are located more peripherally in resting cells (often in contact with the plasma membrane), most do not move centrally following thrombin stimulation as do human platelet granules, and many fuse directly with the external plasma membrane without any intermediate channel. The lack of peripheral location of human granules, their central rather than peripheral movement during secretion, and the presence of extensive channels are all consistent with the larger importance of the secretory channel to human platelets. Thus, though studies of bovine secretion do show that platelets can secrete their granules by direct fusion of granule and surface membranes, other differences from human platelets emphasize that this pathway, although important to bovine platelet secretion, is less important in human platelets. Studies of bovine platelets also show that the OCS is more dynamic than might have been considered from human studies and can form rapidly in response to stimulation. Such newly formed channels are used as a conduit for secretion of granule contents. The finding emphasizes the importance of channels for granule secretion in platelets generally and puts a new perspective on the ability of these cells to form channels rapidly in response to stimulation.

scholarly journals Repression of differentiation genes by Hes transcription factors fuels neural tumour growth in Drosophila

2021 ◽  
Author(s):  
Chrysanthi Voutyraki ◽  
Alexandros Choromidis ◽  
Vasiliki Theodorou ◽  
Christina Efraimoglou ◽  
Gerasimos Anagnostopoulos ◽  
...  
Keyword(s):  
Stem Cell ◽  
Transcription Factors ◽  
Notch Signaling ◽  
Tumour Growth ◽  
Metabolic Reprogramming ◽  
Cell Physiology ◽  
Malignant Tumours ◽  
Rna Profiling ◽  
A Cell

Background: Neural stem cells (NSC) in divide asymmetrically to generate a cell that retains stem cell identity and another that is routed to differentiation. Prolonged mitotic activity of the NSCs gives rise to the plethora of neurons and glial cells that wire the brain and nerve cord. Genetic insults, such as excess of Notch signaling, perturb the normal NSC proliferation programs and trigger the formation of NSC hyperplasias, that can later progress to malignancies. Hes proteins are crucial mediators of Notch signaling and in the NSC context they act by repressing a cohort of early pro-differentiation transcription factors. Downregulation of these pro-differentiation factors makes NSC progeny cells susceptible to adopting an aberrant stem cell program. We have recently shown that Hes overexpression in Drosophila leads to NSC hyperplasias that progress to malignant tumours after allografting to adult hosts. Methods: We have combined genetic analysis, tissue allografting and transcriptomic approaches to address the role of Hes genes in NSC malignant transformation. Results: We show that the E(spl) genes are important mediators in the progression of Notch hyperplasias to malignancy, since allografts lacking the E(spl) genes grow much slower. We further present RNA profiling of Hes-induced tumours at two different stages after allografting. We find that the same cohort of differentiation-promoting transcription factors that are repressed in the primary hyperplasias continue to be downregulated after transplantation. This is accompanied by an upregulation of stress-response genes and metabolic reprogramming. Conclusions: The combination of dedifferentiation and cell physiology changes most likely drive tumour growth.

scholarly journals An analysis of lectin-initiated cell agglutination in a series of CHO subclones which respond morphologically to growth in dibutyryl cyclic AMP.

1976 ◽  
Vol 70 (1) ◽  
pp. 204-216 ◽  
Author(s):  
J van Veen ◽  
R M Roberts ◽  
K D Noonan
Keyword(s):  
Surface Membrane ◽  
Con A ◽  
Cell Agglutination ◽  
Lectin Receptors ◽  
Lectin Receptor ◽  
Free Mobility ◽  
Receptor Sites ◽  
Protein And Rna Synthesis ◽  
A Cell ◽  
Membrane Components

We have investigated the molecular basis of the agglutinability of CHO subclones which respond differentially in terms of morphology and surface architecture in the presence of dB-cAMP in the medium. We have demonstrated that the agglutinability of these subclones with both wheat germ agglutinin (WGA) and concanavalin A (Con A) probably depends on the free lateral mobility of the lectin receptor sites in the plane of the membrane. The nonagglutinable surface architecture seems to depend on the presence in the membrane of a protease-labile peptide(s), which appears to be distinct from the lectin receptors, as well as on continuous protein and RNA synthesis. This dependence on continuous transcription and translation may be related to the maintenance of the protease-labile peptide(s) in such a state as to restrict mobility of the lectin receptors. The surface architecture defined as nonagglutinable also depends on the state of polymerization of the intracellular microtubules and microfilaments. It is suggested that these microskeletal elements serve to anchor the lectin receptors in such a manner as to restrict their mobility and thereby reduce the relative agglutinability of a cell line. We suggest that control of the free mobility of both the Con A and WGA receptor sites is dependent on two constraints, one applied by protease-labile ("surface") membrane components and the other by components of the intracellular microskeletal system.

Detection of α1 Integrin in Urine of Patients With Immunoglobulin A Nephropathy

2008 ◽  
Vol 56 (3) ◽  
pp. 581-586
Author(s):  
Jonathan Bank ◽  
Aharon Ben-David ◽  
Ram Doolman ◽  
Ben-Ami Sela ◽  
Ilan Bank
Keyword(s):  
Mesangial Cells ◽  
Kidney Diseases ◽  
Surface Membrane ◽  
Immunoglobulin A ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dependent Manner ◽  
Healthy Individuals ◽  
Immunoglobulin A Nephropathy ◽  
A Cell ◽  
Dose Dependent

BackgroundThe α1β1 integrin is a cell surface membrane heterodimer composed of noncovalently linked α1 and β1 polypeptides that is up-regulated on activated and proliferating mesangial cells.MethodsA double-sandwich enzyme-linked immunosorbent assay that detects α1 integrin in a specific and dose-dependent manner at concentrations greater than 150 ng/mL was used to evaluate whether intact α1 polypeptides are secreted in the urine samples of 29 patients with various kidney diseases and in those of 5 healthy individuals.Resultsα1 Integrin was detected in 8 of the 29 patients including 3 of 3 patients with biopsy-proven immunoglobulin A nephropathy and 3 of 3 clinically suspected but non-biopsy-proven immunoglobulin A nephropathy with evidence of active nephritis. No α1 integrins were found in samples of 5 healthy controls.Conclusionsα1 Integrin polypeptides can be detected in human urine, particularly in immunoglobulin A nephropathy. Further extensive studies are required to clarify the significance of secretion of α1 integrins in urine of patients with kidney disease.

scholarly journals RDNA-01. TUBULIN AND MICROTUBULES AS MOLECULAR TARGETS FOR TTFIELD THERAPY

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi207-vi207
Author(s):  
Aarat Kalra ◽  
Sahil Patel ◽  
Asadullah Bhuiyan ◽  
Vahid Rezania ◽  
John Lewis ◽  
...  
Keyword(s):  
Electric Fields ◽  
Molecular Targets ◽  
Intermediate Frequency ◽  
Recurrent Glioblastoma ◽  
Charge Storage ◽  
Appreciable Effect ◽  
Recurrent Glioblastoma Multiforme ◽  
Storage Devices ◽  
Ac Electric Fields ◽  
A Cell

Abstract TTField (Tumor-treating field) therapy utilizes low intensity intermediate frequency AC electric fields to reduce the spread of cancer. While it has attained FDA approval for the treatment of recurrent glioblastoma multiforme, the exact molecular targets of TTField therapy are not well understood. Microtubules are pipe-like polymers of the highly charged (–31 e) and strongly dipolar (dipole moment 1666 D) protein, α, β- tubulin. Studies on the electrical properties of microtubules have recently gained interest, with them being modelled as molecular targets of TTFields. Here, we experimentally show that while tubulin polymerized into microtubules leads to an increase in solution capacitance, unpolymerized tubulin has no appreciable effect. To the best of our knowledge, we present the first experimental quantification of the capacitance of a 20 μm-long microtubule. Using these results, we calculate the resonant frequency of a microtubule meshwork in a cell-like environment to be in the TTField regime. Our results utilize high ionic strength solutions and cell-like concentrations of tubulin to show the potential of microtubules as the targets of TTField action and as intracellular charge-storage devices. We conclude with a hypothesis of an electrically-tunable cell, where the dielectric properties of the cytoskeleton alter local and global charge storage and transport.

scholarly journals Actin polymerization and intracellular solvent flow in cell surface blebbing.

1995 ◽  
Vol 129 (6) ◽  
pp. 1589-1599 ◽  
Author(s):  
C C Cunningham
Keyword(s):  
Cell Surface ◽  
Actin Polymerization ◽  
Surface Membrane ◽  
Control Cell ◽  
Cortical Actin ◽  
Final Size ◽  
Actin Structure ◽  
Close Study ◽  
A Cell ◽  
Solvent Flow

The cortical actin gel of eukaryotic cells is postulated to control cell surface activity. One type of protrusion that may offer clues to this regulation are the spherical aneurysms of the surface membrane known as blebs. Blebs occur normally in cells during spreading and alternate with other protrusions, such as ruffles, suggesting similar protrusive machinery is involved. We recently reported that human melanoma cell lines deficient in the actin filament cross-linking protein, ABP-280, show prolonged blebbing, thus allowing close study of blebs and their dynamics. Blebs expand at different rates of volume increase that directly predict the final size achieved by each bleb. These rates decrease as the F-actin concentration of the cells increase over time after plating on a surface, but do so at lower concentrations in ABP-280 expressing cells. Fluorescently labeled actin and phalloidin injections of blebbing cells indicate that a polymerized actin structure is not present initially, but appears later and is responsible for stopping further bleb expansion. Therefore, it is postulated that blebs occur when the fluid-driven expansion of the cell membrane is sufficiently rapid to initially outpace the local rate of actin polymerization. In this model, the rate of intracellular solvent flow driving this expansion decreases as cortical gelation is achieved, whether by factors such as ABP-280, or by concentrated actin polymers alone, thereby leading to decreased size and occurrence of blebs. Since the forces driving bleb extension would always be present in a cell, this process may influence other cell protrusions as well.

scholarly journals BINDING OF SOLUBLE IMMUNE COMPLEXES TO HUMAN LYMPHOBLASTOID CELLS

1974 ◽  
Vol 140 (4) ◽  
pp. 877-894 ◽  
Author(s):  
Argyrios N. Theofilopoulos ◽  
Frank J. Dixon ◽  
Viktor A. Bokisch
Keyword(s):  
Cell Surface ◽  
B Cell ◽  
Cell Lines ◽  
Immune Complexes ◽  
Surface Membrane ◽  
Raji Cells ◽  
Human Lymphoblastoid Cell ◽  
C Cell ◽  
A Cell ◽  
Soluble Immune Complexes

In the present work we studied the expression of membrane-bound Ig (MBIg) as well as receptors for IgG Fc and complement on nine human lymphoblastoid cell lines. When MBIg and receptors for IgG Fc were compared, four categories of cell lines could be distinguished: (a) cell lines having both MBIg and receptors for IgG Fc, (b) cell lines having MBIg but lacking receptors for IgG Fc, (c) cell lines lacking MBIg but having receptors for IgG Fc, and (d) cell lines lacking both MBIg and receptors for IgG Fc. Two types of receptors for complement could be detected on the cell lines studied, one for C3-C3b and one for C3d. When sensitized red cells carrying C3b or C3d were used for rosette tests, three categories of cell lines could be distinguished: (a) cell lines having receptors for C3b and C3d, (b) cell lines having receptors only for C3d and (c) cell lines lacking both receptors. However, when a more sensitive immunofluorescent method was used instead of the rosette technique, it was found that cell lines unable to form rosettes with EAC1423bhu were able to bind soluble C3 or C3b which indicated the presence of these receptors on the cell surface. Inhibition experiments showed that receptors for C3-C3b and receptors for C3d are distinct and that receptors for C3-C3b and C3d are different from receptors for IgG Fc. A cell line (Raji) without MBIg but with receptors for IgG Fc, C3-C3b, and C3d was selected for use in studying the binding mechanism of soluble immune complexes to cell surface membrane. Aggregated human gamma globulin was used in place of immune complexes. Immune complexes containing complement bind to Raji cells only via receptors for complement, namely receptors for C3-C3b and C3d. Binding of immune complexes containing complement to cells is much greater than that of complexes without complement. Immune complexes bound to cells via receptors for complement can be partially released from the cell surface by addition of normal human serum as well as isolated human C3 or C3b. We postulate that such release is due to competition of immune complex bound C3b and free C3 or C3b for the receptors on Raji cells.

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